MEMS accelerometers typically use proof-masses whose displacement is measured by capacitive effect. In order to measure a capacitance, analog components operating at a high frequency are often used. Such components consume significant power. The power consumption of the analog components in a MEMS accelerometer can represent more than 80% of the total consumption.
The article [Varun Kumar et al., “Ultra-Low Power Self-Computing Binary Output Digital MEMS Accelerometer”, MEMS 2016, Shanghai, CHINA, 24-28 January 2016] discloses a MEMS accelerometer producing a binary output, including as many proof-masses as bits to produce. Each proof-mass is suspended from a fixed wall by a spring and is associated with a stop that the proof-mass contacts when the acceleration is sufficient. The stop and the proof-mass are metal-coated, so that the pressure of the proof-mass on the stop closes an electrical contact to represent a binary “1”.
The proof-masses have the same weight and the stiffness constants of the springs follow a geometric progression of ratio 2. With this configuration, a given proof-mass reaches its respective stop under an acceleration twice that causing the previous proof-mass to reach its respective stop. In order to make the provided code binary, the article proposes associating electrostatic actuators to the proof-masses, controlled to lift each proof-mass from its respective stop when a higher rank proof-mass reaches its respective stop.
Such a binary accelerometer, although it does not use analog components to exploit the signal, requires some electrical power to control the actuators. In addition, it is difficult to size the actuators and to produce springs in MEMS technology that have sufficiently accurate stiffnesses following a geometric progression.